I recently received a tankini 2 piece swimsuit that is 80% nylon and 20% spandex. It fits perfect ... but the very top of it is white (the rest of it is black) and I am afraid the top might be "see through" in the water.

I am wanting to dye the entire suit black and have read that acid dyes are best for nylon, but I am afraid to use the hot water, since 20% of the suit is made of spandex. Do you have any recommendations?

Will the white top take to the black dye or look more gray, next to the original black, since the rest of the suit is black?Is 20% spandex a small amount for the heat that is needed?Can I use cooler water?Is it not a good idea to dye a swimsuit due to chlorine and ocean salt? I do actually plan on swimming in this!Might I be better off sewing a better liner in the white part of the suit instead of dying the fabric?

I have never dyed anything before, so I am a complete novice with this!

Looks to me our needs are the more or less same, I wont proceed further unless I get expert recommendations in this. Actually I had a swimsuit and it was having the same problems as you said. Having never used dye before I tried to do all by myself and eventually I made a mess of it. Its not that easier as it looks like. Please provide suggestions, this is a request to the others so that the other ones I have can be utilized to my preferences. Thanks.

If you want to dye a swimsuit, I recommend that you buy a cotton/spandex swimsuit, such as the many different styles sold by Dharma Trading Company. They are not expensive. Cotton can be dyed beautifully and permanently at room temperature, using cool water fiber reactive dyes such as Procion MX dyes, so you do not have to use heat that may damage the spandex.

Unfortunately, nylon, which can be dyed with acid dyes, requires heat in order to bond to dyes; if you compromise by using lower heat so as not to damage the spandex in the bathing suit, the nylon will not dye as permanently or as well. When wetfastness is very important, you probably do not want to compromise on the dyeing temperature for the nylon, but high heat will ruin the spandex.

In the case of the black and white bathing suit with the see-through white top, I think that sewing in a lining for the top part of the suit will produce better and longer-lasting results than trying to dye it black. You will never be able to exactly match one black to the other, anyway. Sewing stores sell bra cups that are designed to be sewn into bathing suits.

I read your blog on acid dyes and I want this to work. I have a yellow one piece that is 90% nylon and 10% spandex. If I did use the high temperatures, with it only being 10% spandex, what will the effects be?